VOCs are found in a wide variety of tail gas produced in chemical plants, and cause significant environmental pollution. As a consequence, environmental regulations around the world seek to strictly control and limit VOC emissions.
Often VOCs are expensive raw materials. Separating and recycling VOCs could help a chemical manufacturer save on the cost of raw materials while meeting environmental regulations.
The following are some of the available commercial technologies for capturing VOCs.
A first known method involves incineration/catalytic decomposition of VOCs, which destroys VOCs, but requires high energy consumption. Another known method requires a refrigeration/cryogenic process to extract the VOCs, which results in a low-purity recovery, and requires high energy consumption. Temperature swing adsorption is another known method, which requires a long operation cycle time, high energy consumption, and may present safety issues.
Currently known PSA processes focus mainly on the recovery of inorganic gas such as H2 and 02, or hydrocarbon mixtures such as gasoline. Due to the chemical complexity of VOCs, VOC-targeted PSA systems in the current commercial market have limited usage, and strongly depend on the pump operating conditions as, for example, disclosed in U.S. Pat. No. 4,857,084. Furthermore, the concentration of VOCs in the emission after PSA cannot satisfy most recent environmental regulations in most countries.